The spun-cotton filtration element of the K&N air filter is oil treated and highly effective at both catching dirt and debris as well as allowing your engine to breath better. "Breath Better" = More HP!
The filter is meant to be cleaned and re-oiled - not replaced - so this is the last air filter you will ever buy. The filter is pre-oiled and ready-to-use right out of the box, and a tube of the special filtration oil comes with it.
This air filter will fit all Porsche® 928 models, but it is not recommended for the LH-Jetronic equipped cars (1985-1995 US) as the oil from the K&N filter may shorten the life of your MAF sensor. This is not a concern on K-Jetronic (CIS) and L-Jetronic equipped cars.